1. Field
Example embodiments relate to a high electron mobility transistor capable of providing an ohmic contact without using a high temperature process.
2. Description of the Related Art
A nitride semiconductor device can be used as, for example, a power device used to control power. A high electron mobility transistor (HEMT) is an example of one of the power devices. An HEMT includes a channel layer and a channel supply layer formed on the channel layer, and the channel layer includes 2-dimensional electron gas (2DEG) that is used as a carrier. Since the 2DEG is used as a carrier, the electron mobility of the HEMT may be higher than general transistors. The HEMT includes a compound semiconductor with a wide band gap. Thus, a breakdown voltage of the HEMT may be higher than general transistors. The breakdown voltage of the HEMT may increase in proportion to the thickness of a compound semiconductor layer including 2DEG, for example, a GaN layer.
The HEMT may include semiconductor layers having different band gaps. A semiconductor layer of the HEMT with a wider band gap acts as a donor. The 2DEG may be generated in a semiconductor layer with a narrower band gap by the semiconductor layer with the wider band gap. In the HEMT, the 2DEG may be used as a channel.
In addition, a high temperature process may be performed in order to reduce the contact resistance when a source electrode and/or a drain electrode makes ohmic contact with the channel supply layer. However, the other semiconductor layers may be damaged by the high temperature process.